Live birds can transmit the disease to humans. ORIN ZEBEST/FLICKR

 On March 30th 2013, the first case of the novel avian influenza A H7N9 virus was reported in China. Since then, there have been 131 confirmed cases of the virus. One hundred and thirty cases have been reported in mainland China and one case was reported in Taiwan. All patients contracted the virus in mainland China. Though most of the infected individuals have recovered, 36 have died and 35 remain in hospital.

Scientists believe that the influenza A H7N9 virus originated from duck and chicken avian influenza viruses. The precise mechanism by which affected individuals contracted the virus is unknown, but it is believed that most human infections occurred because of exposure to domestic poultry or wild birds. Lab tests have indicated that patients became infected at live poultry markets through infected ducks and chickens. It appears to be easier to catch H7N9 from infected birds than H5N1, another strain of influenza that began causing fatalities approximately 10 years ago.

Public health officials have been monitoring the close social circles of infected individuals. Members of these social circles have tended to remain healthy. In a few instances, there were cases of infection in the same family; however, it is unclear whether these cases were due to human-to-human transmission of H7N9 between family members or due to both individuals being exposured to another source. While there isno evidence of widespread human-to-human transmission as of yet, further mutation could give this virus the ability to spread easily between humans. This sustained transmissibility would likely result in another influenza pandemic.

Will H7N9 make its way to Canada?

Dr. Jeff Kwong, scientist at the Institute for Clinical Evaluative Sciences and Public Health Ontario, asserts that “with influenza, anything is possible.” Kwong explains that there is likely asymptomatic spread of the virus between wild and domestic birds, and so “it is possible that the virus may come to Canada via migratory [wild] birds.” He also notes that infected people may themselves bring the virus to Canada, and that “if the virus becomes easily transmissible between humans, given present airline volumes, we will certainly have cases in Canada.”

No new cases have been reported since May 8, 2013. The reason for this decline in number of new cases is not entirely known, but influenza’s inability to spread in the summer as easily as it does in the winter is likely a contributor. Additional steps have been taken to contain the virus: In live-bird markets, all birds are killed if the virus is found, and some markets have been closed down altogether. Despite current control over the spread of H7N9, healthcare authorities around the world have not let their guards down and remain on the lookout for new cases of infection.

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